TRIPOLI, Jan 6 (Reuters) - Libya's armed forces warned they would not allow any oil tanker to load at ports seized by protesters, after the navy blocked a Maltese-flagged vessel from trying to reach one of the docks, Defence Ministry and naval officials said on Monday.

Libya's navy had opened fire on Sunday after the oil tanker tried to approach Es Sider port, which is being held by armed protesters opposed to the central government, officials said in televised news conference.